Atorvastatin, ([R-(R*,R*)]-2-(4-fluorophenyl)-β,δ-dihydroxy-5-(1-methylethyl)-3-phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-heptanoic acid), depicted in lactone form in Formula (I) and its calcium salt trihydrate of Formula (II) (water molecules not shown) are well known in the art, and described, inter alia, in U.S. Pat. Nos. 4,681,893 and 5,273,995, and in U.S. Provisional Patent Application No. 60/166,153, filed Nov. 17, 2000, all of which are herein incorporated by reference.

Three polymorphs of the potassium salt of atorvastatin, namely I, II and III are disclosed in International Patent Publication WO 06/021216, and characterized by X-ray powder diffraction. Form II was described as an amorphous material, while forms I and III were characterized by the following XRPD peaks in degrees 2θ:
Form IForm III8.47.649.09.2610.09.7610.510.1411.2414.116.3816.517.4617.118.1218.4419.9219.7420.9820.3222.0820.8223.2421.3223.8422.9825.224.3427.825.8229.627.3431.328.8432.1630.5636.3437.3242.839.2
Form I was also characterized by a melting peak of 155-165° C. in its DSC. Form II was characterized by a melting peak at 173-183° C. and form III was characterized by a melting peak at 143-156° C. in the DSC.